British Airways has shifted a third of BMI aircraft onto its air operator's certificate, and rebranded them in its own colours as part of the integration effort.
But BA's parent, International Airlines Group, has confirmed that it will close the BMI low-cost operation BMIbaby in early September.
Eight aircraft from the BMI mainline fleet of 25 have been moved to BA.
IAG chief Willie Walsh says that while the integration of BMI has proven "complex" there has been "very good early progress", with no problems that cannot be resolved.
He says the effort is slightly ahead of schedule and that the majority of risk has already been overcome, with more than €100 million ($123 million) in cost reductions, through removal of duplicate activities, identified.
All flights have been moved to BA's sales system and 80% are under BA's commercial control.
"Network flow benefits are already apparent," adds Walsh. The new winter schedule was released in mid-July and each destination on the combined network will operate from a single terminal at London Heathrow.
The transferred aircraft are short-haul types. BA is not taking BMI's Airbus A330s. In addition to the aircraft some 87 pilots and 125 cabin crew have been migrated to BA.
BA completed the employee consultation process for low-cost division BMIbaby at the beginning of August, and IAG says it will "cease operations" on 9 September.
BMI's third component, BMI Regional, was sold to a group of investors earlier this year.